21057037 has 4 divisors (see below), whose sum is σ = 21210876. Its totient is φ = 20903200.

The previous prime is 21057019. The next prime is 21057053. The reversal of 21057037 is 73075012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15515721 + 5541316 = 3939^2 + 2354^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21057037 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21057007) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 76714 + ... + 76987.

It is an arithmetic number, because the mean of its divisors is an integer number (5302719).

Almost surely, 2^21057037 is an apocalyptic number.

It is an amenable number.

21057037 is a deficient number, since it is larger than the sum of its proper divisors (153839).

21057037 is a wasteful number, since it uses less digits than its factorization.

21057037 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153838.

The product of its (nonzero) digits is 1470, while the sum is 25.

The square root of 21057037 is about 4588.7947219286. The cubic root of 21057037 is about 276.1419708229.

The spelling of 21057037 in words is "twenty-one million, fifty-seven thousand, thirty-seven".